Adaptive system and method for automatic tracking of at least one target in at least one video stream

ABSTRACT

A system includes at least one dynamically configurable tracking device, receiving a video stream and, adapted for detection and automatic tracking of at least one target by analysis of the video stream; a calculator of a metric performance value of the tracking device; a configuration parameter corrector of the tracking device as a function of the metric performance value; and a dynamic configurator of the tracking device by applying the corrected configuration parameter. It further includes at least one device for measurement of at least one value representative of a demand for hardware resources by the tracking device, and the calculator is adapted to calculate the metric performance value starting from the measured value.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to French Patent Application No. 1763232, filed Dec. 26, 2017 and French Patent Application No. 1850439, filed Jan. 19, 2018, the entire contents of which are incorporated herein by reference in their entirety.

FIELD

This invention relates to an adaptive system for automatic tracking of at least one target in at least one video stream. It also relates to a corresponding method and computer program.

“Target” means a detectable object or a human or animal living being, to be automatically tracked in the video stream(s) using known methods that can be implemented by micro-programming or micro-wiring in the tracking device that is itself a computer or electronic device. In other words, the target is the object or living being to be situated in real time in space and time from a perception of a scene provided by one or several video cameras.

Application fields include detection and automatic tracking in real time of a target in a video stream, detection and automatic tracking of a target in several video streams supplied in parallel by several cameras (function generally referred to as “real time multi-target tracking”), but also detection and automatic tracking of several targets in several video streams supplied in parallel by several cameras (function generally referred to as “real time multi-target multi-camera tracking”).

BACKGROUND

Multi-target multi-camera tracking in particular is a complex operation requiring the use of sophisticated algorithms generating a large quantity of calculations. It requires the combined and simultaneous use of several electronic components such as CPUs (Central Processing Units), electronic chips specialized in video decoding, graphic processors or GPUs (Graphic Processing Units), etc. Furthermore, algorithms used in the multi-target multi-camera tracking processing chain have a large number of configuration parameters that have an influence on tracking quality and demand on hardware resources.

Furthermore, a very large number of cameras are also frequently used in the field of video surveillance: for example several hundred cameras in closed public places, and up to several thousand or tens of thousands outdoors. A continuous optimization of the compromise between tracking quality and demand on hardware resources then becomes essential, otherwise calculation costs would quickly become prohibitive.

Furthermore, dynamic sharing of hardware resources becomes a major challenge in a context of versatility of these resources. For example, priority can be given at each instant to tracking of a particular target, and even temporarily reducing the quality of other tracking. In order to achieve this flexibility, it must be possible to continuously adapt tracking so that it functions with predetermined optimization aimed at reducing the demand on hardware resources while maintaining a certain quality level.

An adaptive system for automatic tracking of a target in at least one video stream is for example envisaged in the paper by Igual et al, entitled “Adaptive tracking algorithms to improve the use of computing resources”, published in IET Computer Vision, volume 7, No. 6, pages 415 to 424 (2013). It is designed to detect tracking risk situations, in other words situations in which the tracking device(s) is or are liable to make detection or tracking errors, to automatically adapt calculation capacities (i.e. demand on hardware resources) or to change the tracking algorithm. To achieve this, it is capable of calculating at least one metric performance value starting from a target tracking result supplied by the tracking device(s) and making use of it to dynamically adapt its configuration parameters.

But this makes the tracking system into an adaptive system slaved to the performances of the tracking device(s), which is not what is wanted in all situations.

SUMMARY

It may thus be desirable to design an adaptive system for automatic target tracking in at least one video stream capable of overcoming at least some of the above mentioned problems and constraints.

Therefore, in an aspect of the invention, an adaptive system for automatic tracking of a target in at least one video stream is proposed, comprising:

-   -   at least one dynamically configurable tracking device receiving         the at least one video stream, adapted for detection and         automatic tracking of at least one target by analysis of the at         least one video stream,     -   a calculator to determine at least one metric performance value         of the at least one tracking device,     -   a corrector of at least one configuration parameter of the least         one tracking device as a function of the at least one metric         performance value,     -   at least one dynamic configurator of the at least one tracking         device by application of the at least one corrected         configuration parameter, and     -   at least one device for measuring at least one value         representative of a demand for hardware resources by the at         least one tracking device,         the calculator being adapted more precisely to calculate the at         least one metric performance value from the at least one         measured value.

Thus, the system becomes slaved mainly to hardware resources, so that its processing can genuinely be optimized within the limit of its resources.

Optionally, an adaptive automatic target tracking system according to an embodiment of the invention may also comprise at least one video capture device connected in data transmission to the at least one tracking device to supply the at least one video stream.

Also optionally, each tracking device can be configured using at least one of the configuration parameters of the set composed of:

-   -   a number of images to be processed or interpreted per second in         the at least one video stream,     -   an image resolution, and     -   a maximum number of targets to be detected and tracked in the at         least one video stream.

Also optionally, the at least one measurement device is adapted to measure at least one of the values of the set composed of:

-   -   an operating frequency of central hardware and/or graphic         processing units on demand by the at least one tracking device,     -   a usage ratio of allocated memory space for the at least one         tracking device,     -   a data input or output flow rate to/from the at least one         tracking device,     -   a number of images processed or interpreted per second in the         video stream by the at least one tracking device, and     -   a number of calculation cores used in the central hardware         and/or graphic processing units on demand by the at least one         tracking device,

Also optionally, the calculator is more precisely adapted to calculate the at least one metric performance value in the form of at least one of the values of the set composed of:

-   -   a fraction of the maximum operating frequency of central         hardware and/or graphic processing units on demand by the at         least one tracking device,     -   the usage ratio of allocated memory space for the at least one         tracking device,     -   a fraction of the maximum data input or output flow rate to/from         the at least one tracking device,     -   a result metric obtained relative to an objective set for the         number of images processed or interpreted per second in the         video stream by the at least one tracking device,     -   a usage ratio of the calculation cores used in the central         hardware and/or graphic processing units on demand by the at         least one tracking device.

Also optionally, the calculator is more precisely adapted to calculate a number of images processed or interpreted per second in the at least one video stream by the at least one tracking device from a list of time-dating values that it receives, at which the at least one tracking device starts and finishes its processing cycles of the at least one video stream.

Also optionally, an adaptive automatic target tracking system according to an embodiment of the invention may comprise several tracking devices, simultaneously receiving several video streams respectively.

Also optionally, each tracking device is adapted for detection and simultaneous automatic tracking of several targets by analysis of the video stream that it receives.

In an aspect of the invention, an adaptive method for automatic tracking of a target in at least one video stream is also proposed, comprising the following steps:

-   -   analyze the at least one video stream using at least one         dynamically configurable tracking device adapted for detection         and automatic tracking of at least one target in the at least         one video stream,     -   calculate at least one metric performance value of the at least         one tracking device,     -   correct at least one configuration parameter of the at least one         tracking device as a function of the at least one metric         performance value, and     -   dynamic configuration of the at least one tracking device by         application of the at least one corrected configuration         parameter.         the method further comprising the measurement of at least one         value representative of a demand by the at least one tracking         device for hardware resources, and the at least one metric         performance value being calculated from the at least one         measured value.

In an aspect of the invention, a computer program that can be downloaded from a communication network and/or saved on a non-transitory computer readable medium or support that can be read by a computer and/or executed by a processor is also proposed, comprising machine readable instructions for the execution of steps in an adaptive method for automatic target tracking in at least one video stream according to the invention, when the program is run on a computer.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood with reference to the following description, given purely as an example, with reference to the appended drawings in which:

FIG. 1 diagrammatically represents the general structure of an adaptive system for automatic target tracking in at least one video stream, according to an embodiment of the invention,

FIG. 2 illustrates the successive steps in an automatic target tracking method implemented by the system in FIG. 1,

FIG. 3 diagrammatically represents an example of a first simplified architecture for the system in FIG. 1, and

FIG. 4 diagrammatically represents an example of a second shared and decoupled architecture for the system in FIG. 1.

DETAILED DESCRIPTION

The adaptive automatic target tracking system in FIG. 1 comprises at least one video capture device for the supply of at least one video stream. In the non-limitative example illustrated, it comprises n, more precisely n video cameras 10 ₁, . . . , 10 _(i), . . . , 10 _(n) for the supply of n video streams. Each of them films a scene and transmits the corresponding video stream through a computer connection.

It further comprises a collector 12 of the n video streams to transmit them to a primary stage of tracking devices adapted for detection and automatic tracking of at least one target by analysis of video streams that they respectively receive.

In the example illustrated, the primary stage comprises:

-   -   n tracking devices 14 ₁, . . . , 14 _(i), . . . , 14 _(n) for         respective processing of the n video streams output from the n         video cameras 10 ₁, . . . , 10 _(i), . . . , 10 _(n), and         transmitted by the collector 12, and     -   according to a first aspect of this invention, a supplementary         reference tracking device 14 _(MSTR) for processing of         respective portions of the n video streams output from the n         video cameras 10 ₁, . . . , 10 _(i), . . . , 10 _(n), these         portions being selected and transmitted by the collector 12.

Each of the n tracking devices 14 ₁, . . . , 14 _(i), . . . , 14 _(n) is for example capable of detecting and simultaneously tracking several targets in real time that can be seen in the video stream that it receives. Such devices (hardware and software) are well known in prior art and will not be described further. They can be configured dynamically using one or several parameters that influence their consumption of hardware resources, their performances and the quality of their target tracking results: for example, a number of images to be processed or interpreted per second in the video stream, an image resolution, a maximum number of targets to be detected and tracked in the video stream, etc. The dynamic configuration consists of being able to modify these configuration parameters during execution. To achieve this, they are associated with n dynamic configurators 16 ₁, . . . , 16 _(i), . . . , 16 _(n) respectively that are designed in hardware or programmed in software to store, adjust and dynamically apply these configuration parameters.

According to a second aspect of this invention, they are also associated with n measurement devices 18 ₁, . . . , 18 _(i), . . . , 18 _(n) respectively that are designed by hardware or programmed by software to measure one or several values representative of a demand for or use of hardware resources by the n tracking devices 14 ₁, . . . , 14 _(i), . . . , 14 _(n). These values may comprise an operating frequency of CPU and GPU hardware units on demand, a usage ratio of allocated memory space, a data input or output flow, a number of images processed or interpreted per second in the video stream, a number of calculation cores used in the CPU and GPU hardware units on demand, etc.

It will be noted that the number of images processed or interpreted per second in the video stream is a parameter than can be both configured (using the n dynamic configurators 16 ₁, . . . , 16 _(i), . . . , 16 _(n)) and measured (using the n measurement devices 18 ₁, . . . , 18 _(i), . . . , 18 _(n)). Fixing an objective consisting of processing or interpreting a given number of images per second using one of the configurators 16 ₁, . . . , 16 _(i), . . . , 16 _(n) does not necessarily mean that it will be achieved. In particular, this objective can be temporarily hampered by insufficient hardware resources and it is beneficial to be able to measure it.

Thus, by dynamically varying the configuration parameters and regularly measuring the demand for hardware resources, it becomes genuinely possible to automatically optimize processing done by the n tracking devices 14 ₁, . . . , 14 _(i), . . . , 14 _(n) within the limit of available resources.

Video stream portions transmitted to the supplementary reference tracking device 14 _(MSTR) are selected successively by the collector 12 using a predetermined arbitrary selection algorithmic rule, for example according to a periodic scheduling of the n video cameras 10 ₁, . . . , 10 _(i), . . . , 10 _(n). In the example in FIG. 1, n portions P₁, . . . , P_(i), . . . , P_(n) are successively selected and extracted from the n video streams supplied by the n video cameras 10 ₁, . . . , 10 _(i), . . . , 10 _(n). Each is beneficially sufficiently short duration to not constrain the supplementary reference tracking device 14 _(MSTR) to processing in real time. For example, the duration of each video stream portion may be less than one tenth, or even a hundredth, of the time allowed to the supplementary reference tracking device 14 _(MSTR) to make its analysis. Thus the latter device, unlike the n tracking devices 14 ₁, . . . , 14 _(i), . . . , 14 _(n), can have higher performance, remote, . . . , hardware resources both in terms of memory and calculation capacity. Therefore it can be considered that the detection and tracking processing done by the supplementary reference tracking device 14 _(MSTR) is optimal, or at least that its quality and resource levels are better than the n tracking devices 14 ₁, . . . , 14 _(i), . . . , 14 _(n). This is why the results provided by this supplementary reference tracking device 14 _(MSTR) can be considered to form a reference, without any target detection or tracking error, with which the results output by the n tracking devices 14 ₁, . . . , 14 _(i), . . . , 14 _(n) can be compared, according to the first aspect of this invention.

The adaptive automatic target tracking system in FIG. 1 further comprises a metrics calculator 20 designed in hardware or programmed in software to calculate at least one metric performance value for each of the tracking devices 14 ₁, . . . , 14 _(i), . . . , 14 _(n).

According to the first aspect of this invention, the metrics calculator 20 comprises a first hardware or software module 22 adapted more precisely to calculate a first performance metric value from a comparison on each of the n video stream portions P₁, . . . , P_(i), . . . , P_(n), of target tracking results R₁, . . . , R_(i), . . . , R_(n) output by the tracking devices 14 ₁, . . . , 14 _(i), . . . , 14 _(n) respectively on the n portions P₁, . . . , P_(i), . . . , P_(n) with the target tracking results S₁, . . . , S_(i), . . . , S_(n) supplied successively by the supplementary reference tracking device 14 _(MSTR) on these same n portions P₁, . . . , P_(i), . . . , P_(n). The first metric performance value can be expressed in the form of a ratio and can be correlated to a number of interchanged targets or a number of targets not identified by each of the n tracking devices 14 ₁, . . . , 14 _(i), . . . , 14 _(n) when they are compared with the supplementary reference tracking device 14 _(MSTR).

According to the second aspect of this invention, the metrics calculator 20 comprises a second hardware or software module 24 adapted more precisely to calculate at least one second metric performance value starting from each value representative of demand for hardware resources supplied by the n measurement devices 18 ₁, . . . , 18 _(i), . . . , 18 _(n). As for the measurements given above as examples, it can thus be a fraction of the maximum operating frequency of the CPU and GPU hardware units on demand, a usage ratio of allocated memory space, a fraction of the maximum data input or output flow, a metric of an obtained result related to an objective set in terms of the number of images processed or interpreted per second, a usage ratio of calculation cores used in the CPU and GPU hardware units on demand compared with a maximum allocated number, for each of the n tracking devices 14 ₁, . . . 14 _(i), . . . , 14 _(n).

The adaptive automatic target tracking system in FIG. 1 further comprises a corrector 26 adapted in hardware or programmed in software to recalculate the configuration parameters for the n tracking devices 14 ₁, . . . , 14 _(i), . . . , 14 _(n) starting from the metric values supplied by the metrics calculator 20. In practice, this corrector 26 may have predetermined functions or systems of linear or non-linear equations, a rules motor, an expert system, a neuron networks system, comparators, or any other artificial intelligence system useful for updating configuration parameters of each of the tracking devices 14 ₁, . . . , 14 _(i), . . . , 14 _(n). In particular, it may be a set of rules or laws that have to be observed, such as a law according to which each tracking device 14 ₁, . . . , 14 _(i), . . . , 14 _(n) must process at least five images per second, or a law according to which each tracking device 14 ₁, . . . , 14 _(i), . . . , 14 _(n) must not fail to detect more than 30% of targets.

It may use an individual approach by giving priority to the individual adjustment of each of the n tracking devices 14 ₁, . . . , 14 _(i), . . . , 14 _(n), but also a global approach, giving priority to equitably distributing globally available hardware resources as a function of the different needs of each. It provides its results to the n dynamic configurators 16 ₁, . . . , 16 _(i), . . . , 16 _(n).

The supplementary reference tracking device 14 _(MSTR), the metrics calculator 20 and the corrector 26 form a hardware or software optimization platform 28 for the system in FIG. 1.

The n results of the n tracking devices 14 ₁, . . . , 14 _(i), . . . , 14 _(n) are supplied to a secondary stage 30 of the adaptive automatic target tracking system in FIG. 1. In a simple embodiment, this secondary stage can be a system output stage, but it can also be a secondary supplementary video stream processing stage.

Operation of the system described above will now be described with reference to FIG. 2.

In a first step 100, the collector 12 transmits the n video streams supplied by the n video cameras 10 ₁, . . . , 10 _(i), . . . , 10 _(n) to the n tracking devices 14 ₁, . . . , 14 _(i), . . . , 14 _(n) of the primary stage of the system for analysis. During this first step, the collector 12 transmits the n successive video stream portions P₁, . . . , P_(i), . . . , P_(n) to the supplementary reference tracking device 14 _(MSTR) also for analysis.

During the next step 102, each of the n tracking devices 14 ₁, . . . , 14 _(i), . . . , 14 _(n) becomes familiar with its current configuration using its dynamic configurator 16 ₁, . . . , 16 _(i), . . . , 16 _(n), analyses the video stream transmitted to it and sends its results to the secondary stage 30. It also supplies its partial results R₁, . . . , R_(i), . . . , R_(n) obtained on the video stream portions P₁, . . . , P_(i), . . . , P_(n) to the first module 22 of the metrics calculator 20.

During a step 104 executed in parallel to step 102, the supplementary reference tracking device 14 _(MSTR) analyses the n successive portions P₁, . . . , P_(i), . . . , P_(n) of video stream transmitted to it and outputs its results S₁, . . . , S_(i), . . . , S_(n) to the first module 22 of the metrics calculator 20.

Subsequent to steps 102 and 104, the first module 22 of the metrics calculator 20 calculates its above-mentioned metric values and supplies them to the corrector 26 during a step 106.

During a step 108 executed in parallel to steps 102 and 104, each of the n measurement devices 18 ₁, . . . , 18 _(i), . . . , 18 _(n) supplies its measured values to the second module 24 of the metrics calculator 20.

Subsequent to step 108, the second module 24 of the metrics calculator 20 calculates its above-mentioned metric values and supplies them to the corrector 26 during a step 110.

Subsequent to steps 106 and 110, the corrector 26 updates the configuration parameters of then tracking devices 14 ₁, . . . , 14 _(i), . . . , 14 _(n) as indicated previously during a step 112. It transmits updated values to the dynamic configurators 16 ₁, . . . , 16 _(i), . . . , 16 _(n).

During a last step 114, each dynamic configurator 16 ₁, . . . , 16 _(i), . . . , 16 _(n) acts on each tracking device 14 ₁, . . . , 14 _(i), . . . , 14 _(n) respectively, as indicated above.

Steps 100 to 114 are beneficially executed continuously, all the time that the system is in operation.

Concerning the metrics calculator 20, as a non-limitative specific example:

-   -   its second module 24 can receive, as an input, a list of         time-date values (dates, times, etc.) respectively supplied by         the n measurement devices 18 ₁, . . . , 18 _(i), . . . , 18         _(n), at which then tracking devices 14 ₁, . . . , 14 _(i), . .         . , 14 _(n) start and end their processing cycles for a given         image,     -   its first module 22 can receive, as an input, a list containing         detected targets with associated spatial coordinates for each of         the n tracking devices 14 ₁, . . . , 14 _(i), . . . , 14 _(n)         and a corresponding reference list containing detected targets         with associated spatial coordinates for the supplementary         reference tracking device 14 _(MSTR).

Starting from these input data:

-   -   the second module 24 can calculate a real operating frequency of         each of n tracking devices 14 ₁, . . . , 14 _(i), . . . , 14         _(n), in other words the number of images actually processed or         interpreted per second in the video stream by each tracking         device,     -   the first module 22 can calculate a number of targets lost in a         scene of the video stream by each of the n tracking devices 14         ₁, . . . , 14 _(i), . . . , 14 _(n), by comparing the size of         the reference list mentioned above with the size of each of the         lists of detected targets supplied by the n tracking devices 14         ₁, . . . , 14 _(i), . . . , 14 _(n), and     -   the first module 22 can calculate a number of targets badly         localized in a scene of the video stream by each of the n         tracking devices 14 ₁, . . . , 14 _(i), . . . , 14 _(n), by         comparing the spatial coordinates of the reference list         mentioned above with each of the spatial coordinates of the         lists of detected targets supplied by the n tracking devices 14         ₁, . . . , 14 _(i), . . . , 14 _(n): for example for each         tracking device, all targets detected by this tracking device         and also by the supplementary reference tracking device 14         _(MSTR) for which the localizations are different by more than a         certain percentage (for example 5%) of the size of images are         counted.

Concerning the corrector 26, as a non-limitative specific example, its input may receive the results of the above-mentioned calculations made by the first and second modules 22, 24 and a set quality, in other words a minimum quality to be maintained.

Starting from these input data, it may, among other options, regulate the operating frequency of each of the n tracking devices 14 ₁, . . . , 14 _(i), . . . , 14 _(n), called “set frequency” or number of images to be processed or interpreted per second, by application of rules such as the following rules:

-   -   if the number of lost targets added to the number of badly         localized targets is higher than the set quality, for example         increased by a predetermined tolerance value, then the set         frequency of the tracking device considered should be increased,         and the global distribution of hardware resources between the n         tracking devices 14 ₁, . . . , 14 _(i), . . . , 14 _(n) may need         to be revised,     -   if the number of lost targets added to the number of badly         localized targets is lower than the set quality, for example         reduced by the predetermined tolerance value, then the set         frequency of the tracking device considered should be reduced,         and the global distribution of hardware resources between the n         tracking devices 14 ₁, . . . , 14 _(i), . . . , 14 _(n) may need         to be revised,

As a specific non-limitative example, the revision of the global distribution of hardware resources may apply the following rules:

-   -   the n tracking devices 14 ₁, . . . , 14 _(i), . . . , 14 _(n)         are classified by quality level: for example level 4 if the         number of lost targets added to the number of badly localized         targets is between 0 and 4, level 3 if the number of lost         targets added to the number of badly localized targets is         between 5 and 8, level 2 if the number of lost targets added to         the number of badly localized targets is between 9 and 12, and         level 1 if the number of lost targets added to the number of         badly localized targets is higher than 12,     -   if two tracking devices have the same quality level, then each         has the right to an equally high operating frequency,     -   if the quality level of one tracking device is lower than         another, then it has the right to a higher operating frequency         than the other, and     -   if the quality level of one tracking device is higher than         another, then it has the right to a lower operating frequency         than the other.

A first example of a simple implementation of the system in FIG. 1 is illustrated on FIG. 3. This architecture has components for which the control and cost make implementation easy.

A tracking server 40, for example forming a classical computer with an operating system such as Linux (registered trademark) and a network access card, comprises a set 42 of shared tracking devices. This set 42 receives video streams from the n video cameras 10 ₁, . . . , 10 _(i), . . . , 10 _(n) that can be in the form of IP (Internet Protocol) cameras or cameras conforming with the Wi-Fi standard protocol transmitting their video streams through the network. The tracking devices are simply software components capable of executing several target detection and tracking algorithms, for example implemented in the C++ or Python (registered trademark) programming language with the assistance of the OpenCV (registered trademark) software library.

The optimization platform 28 is also implemented in a classical computer with access to the network. The supplementary reference tracking device 14 _(MSTR), the metrics calculator 20 and the corrector 26 that compose it are also software components, for example implemented in the C++ or Python (registered trademark) programming language with the assistance of the OpenCV (registered trademark) software library. In particular, the metrics calculator 20 and the corrector 26 can be programmed using algorithms according to prior art to calculate metrics and corrections based on simple equations tested on test data for regulation. Also in this example, the supplementary reference tracking device 14 _(MSTR) receives the portions of video streams from the set 42 of shared tracking devices.

A second more complex but more flexible implementation of the system in FIG. 1 is illustrated on FIG. 4. This architecture enables sharing and decoupling of all its components, so as to envisage an industrial implementation with the capacity to process a very large number of video cameras. In particular, the effect of scale or scalability in this type of architecture can create a considerable improvement in the efficiency of the system by benefiting from multiplying the gains by video cameras and the use of inexpensive calculation units shared for optimization through calculations of metrics and corrections.

A first component 50, acting as a distributor and a communication bus, receives video streams from the n video cameras 10 ₁, . . . , 10 _(i), . . . , 10 _(n). It may be a message broker type component such as Apache ActiveMQ (registered trademark) or WebSphere (registered trademark), or an ESB (“Enterprise Service Bus”) such as Blueway (registered trademark) or Talend (registered trademark).

A second component 52 connected to the first component 50, has an IaaS (“Infrastructure as a Service”) infrastructure on demand type evolutive architecture, by which it is possible to dynamically allocate calculation units such as virtual machines to adapt to the demand for resources. This second component 52 may be implemented in private IaaS based on VMware components (registered trademark) or in public IaaS based on services such as Amazon EC2 (registered trademark). It comprises a tracking module 54 with M tracking devices 54 ₁, . . . , 54 _(M), a reference tracking module 56 with N supplementary reference tracking devices 56 ₁, . . . , 56 _(N) and a regulation module 58 with P regulators 58 ₁, . . . , 58 _(P) each comprising a metrics calculator and a corrector. These three modules 54, 56 and 58 are deployed on a virtual machine.

Data exchanges between the first and second components 50 and 52 take place as follows:

-   -   transmission of video streams and corrected configuration         parameters, from the first component 50 to the tracking module         54 of the second component 52,     -   transmission of video tracking results, from the tracking module         54 of the second component 52 to the first component 50,     -   transmission of selected portions of video streams, from the         first component 50 to the reference tracking module 56 of the         second component 52,     -   transmission of reference tracking results on selected portions         of video streams, from the reference tracking module 56 of the         second component 52 to the first component 50,     -   transmission of video tracking results and reference tracking         results, from the first component 50 to the regulation module 58         of the second component 52,     -   exchange of metric values between regulators of the regulation         module 58 of the second component 52 passing through the first         component 50,     -   transmission of corrected configuration parameters, from the         regulation module 58 of the second component 52 to the first         component 50,     -   transmission of video tracking results from the first component         50 to a secondary or output stage.

The distribution of tasks within each of the modules 54, 56 and 58 is done in a decoupled manner depending on the availability and the resources of their components 54 ₁, . . . , 54 _(M), 56 ₁, . . . , 56 _(N) and 58 ₁, . . . , 58 _(P).

As mentioned above, the systems illustrated on FIGS. 1, 3 and 4 can be used in computer devices such as classical computers comprising processors associated with memories for the storage of data files and computer programs. Tracking and regulation devices (by calculation of metrics, correction and configuration) can be implemented in these computers in the form of computer programs or different functions of the same computer program. These functions could also be at least partly micro-programmed or microwired in dedicated integrated circuits. Thus as a variant, the computer devices implementing FIGS. 1, 3 and 4 could be replaced by electronic devices composed solely of digital circuits (with no computer program) to perform the same actions.

It clearly appears that an adaptive system for automatic target tracking in at least one video stream like those described above can genuinely automatically optimize its processing within the limit of its resources and detect risk situations much more reliably. The resulting optimization of hardware resources largely compensates the extra cost generated by addition of the reference tracking device(s) and devices for measuring the demand for hardware resources.

In particular, it becomes possible to minimize the hardware occupancy ratio for the global system including all tracking devices and to maximize the tracking quality for each device: the regulation chain by calculation of metrics and corrections is indeed advantageously used regularly, for example periodically, for each tracking device of the primary stage so that operation thereof can be corrected regularly as a function of objectives set for the system.

The supplementary reference tracking device(s) is (are) not affected by real time processing constraints because the frequency and latency of regulation loops can vary without causing any sudden deterioration to performance of the system. Thus, each supplementary reference tracking device can be deployed on physical components shared with other functions of the system, in a generally less expensive architecture, relative to the total cost per unit operation, than real time oriented architectures.

The global cost of the system depends on the complexity of scenes and the expected quality of tracking devices. The following reasoning shows that this invention reduces expenditure of the system, for a set tracking quality. A similar reasoning may be adopted by which this invention improves the tracking quality, for a given expenditure.

Note:

-   -   ct_(regulation-for-i) the quantity of hardware resources used         for the regulation (metric and correction calculations) of the         tracking device 14 _(i),     -   ct_(track-master-tracker-i), ct_(calculate-metrics-i),         ct_(corrector-i) the quantity of hardware resources used for         evaluation by the supplementary reference tracking device 14         _(MSTR) of video stream portions from camera 10 _(i), the         evaluation of resource consumption by tracking device 14 _(i),         the correction calculation to be applied to the tracking device         14 _(i),     -   ct_(ave-unit-tracker) the average quantity of hardware resources         requested by a tracking device (average calculated on all         tracking devices 14 i to 14 _(n)),     -   ct_(ave-master-unit-tracker) the quantity of hardware resources         required for evaluation by the supplementary reference tracking         device 14 _(MSTR) of video stream portions from a camera         averaged over a period and for all tracking devices,     -   ct_(optimized-ave-unit-tracker) the average quantity of hardware         resources requested by a tracking device when the previously         described regulation is used (average calculated on all tracking         devices 14 ₁ to 14 _(n)),

When the system benefits from the first and second aspects of this invention:

${ct}_{{optimized}\text{-}{primary}\text{-}{trackers}\text{-}{stage}} = {\sum\limits_{i = 1}^{n}\; \left( {{ct}_{{unit}\text{-}{tracker}\text{-}i} + {ct}_{{regulation}\text{-}{for}\text{-}i}} \right)}$ and ct_(regulation-for-i) = ct_(track-master-tracker-i) + ct_(calculate-metrics-i) + ct_(corrector-i)

For a simple implementation of the regulation:

     ct_(regulation-for-i) ≈ ct_(track-master-tracker-i) ${ct}_{{optimized}\text{-}{primary}\text{-}{trackers}\text{-}{stage}} = {\sum\limits_{i = 1}^{n}\; \left( {{ct}_{{unit}\text{-}{tracker}\text{-}i} + {ct}_{{track}\text{-}{master}\text{-}{tracker}\text{-}i}} \right)}$ ct_(optimized-primary-trackers-stage) = n × (ct_(optimized-ave-unit-tracker) + ct_(ave-master-unit − tracker))

When the system does not benefit from the first and second aspects of this invention:

ct _(primary-trackers-stage) =n×ct _(ave-unit-tracker)

Hence a gain G:

G=ct _(primary-trackers-stage) −ct _(optimized-primary-trackers-stage)

gain=n×(ct _(ave-unit-tracker) −ct _(optimized-ave-unit-tracker) −ct _(ave-master-unit-tracker))

Therefore this invention offers a better performance when the average optimization for a tracking device resulting from the regulation is higher than average expenses induced by the supplementary reference tracking device for a tracking device:

ct _(ave-unit-tracker) −ct _(optimized-ave-unit-tracker) >ct _(ave-master-unit-tracker)

It will also be noted that the invention is not restricted to the embodiments described above.

In particular, the embodiments described above combine the advantages of the first and second aspects of this invention. But it should be noted that these two aspects are independent of each other. A system according to the first aspect of this invention may not include measurement devices and calculations of the second metric values. A system according to the second aspect of this invention may not include the supplementary reference tracking device(s) and calculations of the first metric values.

It will more generally be clear to an expert in the field that various modifications can be made to the embodiments described above, making use of the information disclosed above. The terms used in the detailed presentation of the invention given above must not be interpreted as limiting the invention to the embodiments presented in this description, but must be interpreted to include all equivalents that can be designed by those skilled in the art applying their own general knowledge to implementation of the information disclosed above. 

1. An adaptive system for automatic tracking of a target in at least one video stream, comprising: at least one dynamically configurable tracking device, receiving said at least one video stream, adapted for detection and automatic tracking of at least one target by analysis of said at least one video stream, a calculator to determine at least one metric performance value of said at least one tracking device, a corrector of at least one configuration parameter of said least one tracking device as a function of said at least one metric performance value, at least one dynamic configurator of said at least one tracking device by application of said at least one corrected configuration parameter, and at least one device for measurement of at least one value representative of a demand for hardware resources by said at least one tracking device, wherein the calculator is adapted to calculate said at least one metric performance value starting from said at least one measured value.
 2. The adaptive system for automatic target tracking according to claim 1, further comprising at least one video capture device, connected in data transmission to said at least one tracking device to supply said at least one video stream.
 3. The adaptive automatic target tracking system according to claim 1, wherein each tracking device is configurable using at least one of the configuration parameters of the set composed of: a number of images to be processed or interpreted per second in said at least one video stream, an image resolution, and a maximum number of targets to be detected and tracked in said at least one video stream.
 4. The adaptive automatic target tracking system according to claim 1, wherein said at least one measurement device is adapted to measure at least one of the values of the set composed of: an operating frequency of central hardware and/or graphic processing units on demand by said at least one tracking device, a usage ratio of allocated memory space for said at least one tracking device, a data input or output flow rate to/from said at least one tracking device, a number of images processed or interpreted per second in the video stream by said at least one tracking device, and a number of calculation cores used in the central hardware and/or graphic processing units on demand by said at least one tracking device.
 5. The adaptive system for automatic target tracking according to claim 4, wherein the calculator is adapted to calculate said at least one metric performance value in the form of at least one of the values of the set composed of: a fraction of the maximum operating frequency of central hardware and/or graphic processing units on demand by said at least one tracking device, the usage ratio of allocated memory space for said at least one tracking device, a fraction of the maximum data input or output flow rate to/from said at least one tracking device, a result metric obtained relative to an objective set for the number of images processed or interpreted per second in the video stream by said at least one tracking device, a usage ratio of the calculation cores used in the central hardware and/or graphic processing units on demand by said at least one tracking device.
 6. The adaptive system for automatic target tracking according to claim 1, wherein the calculator is adapted to calculate a number of images processed or interpreted per second in said at least one video stream by said at least one tracking device from a list of time-dating values that it receives, at which said at least one tracking device starts and finishes its processing cycles of said at least one video stream.
 7. The adaptive automatic target tracking system according to claim 1, comprising several tracking devices, simultaneously receiving respectively several video streams.
 8. The adaptive automatic target tracking system according to claim 1, wherein each tracking device is adapted for detection and simultaneous automatic tracking of several targets by analysis of the video stream that it receives.
 9. An adaptive method for automatic tracking of a target in at least one video stream, comprising: analyzing said at least one video stream using at least one dynamically configurable tracking device adapted for detection and automatic tracking of at least one target in said at least one video stream, calculating at least one metric performance value of said at least one tracking device, correcting at least one configuration parameter of said at least one tracking device as a function of said at least one metric performance value, dynamic configuring said at least one tracking device (14 ₁, . . . , 14 _(n)) by application of said at least one corrected configuration parameter, and measuring at least one value representative of a demand by said at least one tracking device for hardware resources, wherein the calculation of the at least one metric performance value is made from said at least one measured value.
 10. A non-transitory computer readable medium including a program comprising machine readable instructions for the execution of steps in an adaptive method for automatic tracking of a target in at least one video stream according to claim 9, when said program is run on a computer. 